For many years it has been common practice to increase one's strength and endurance or to speed recovery from an injury by doing work against a resistance force. Possibly the simplest apparatus for this purpose is bar- or dumbbells which are useful in the exercise of the arms and upper body. However, the use of dumbbells is not totally desirable because they are free weights; that is, the athlete is not constrained to use them in the most efficient possible manner. Moreover, there are safety considerations which militate against the use of such free weights.
An attempt at solving this problem was the development of the apparatus known as the "Universal Gym". This features a central station with a plurality of stacks of weights riding up and down on guide rods. The weights are lifted by the athlete through a complicated system of cables running over pulleys and, in the case of certain muscle groups, by lever action provided by rotation of a rigid rod. A comparable apparatus is shown in U.S. Pat. No. 3,850,431 to Winans. The lever action-type exercises are an improvement over barbells in that the path undergone by the exercised body portion during the exercise is defined by the rigidity and fixed pivot point of the lever, thus ensuring that the athlete will exhibit "good form" during his exercise. However, the Universal Gym and the Winans approaches, as described above, both also use flexible cables connected to handles. When exercising using these devices the athlete is not constrained to the proper or most efficient mode of exercise. Too, some desirable exercises, particularly those for the lower back, are not provided by either apparatus. Furthermore, the Universal Gym has not been designed to ensure efficient utilization of weights, so that if a complete exercise program is to be undergone using Universal Gym apparatus, a complete apparatus must be purchased which entails the purchase of duplicative quantities of weights, thus rendering it not suitable for home but more useful in the gymnasium environment, where a number of athletes may utilize the apparatus simultaneously. The Winans approach is meant to be economically feasible for home use, but lacks versatility in the exercises which can be performed.
More recently a new class of exercise apparatus has been available. This apparatus, sold under the tradename "Nautilus", comprises a series of machines, each designed to exercise one or, at most, two muscles or groups of muscles. The Nautilus machines are very elaborately designed and feature rigid members rotatable by the athlete in doing exercises so that good conformation is assured; the members generally pivot about the axis of the joint the muscles of which are being exercised. See, e.g., U.S. Pat. No. 3,640,527 to Proctor. Moreover, most of the Nautilus machines feature variation of the mechanical advantage provided to the athlete during the travel of the rotatable member through its arc. Such a machine is described in U.S. Pat. No. 4,200,279 to Lambert. This, it is stated, provides better exercise as compared to, e.g., the lifting of a barbell by an athlete exercising a bicep, wherein the work done against the force of gravity per degree of forearm rotation decreases as the athlete's forearm becomes more nearly vertical. However, as in the case of the Universal Gym, the very complexity of the Nautilus apparatus renders it entirely uneconomical for use by an athlete at home, since a complete Nautilus system comprises many machines, each costing several thousands of dollars and requiring a great deal of floor space. Accordingly, the Nautilus system, while of considerable utility, is impractical for use by a single athlete and therefore its use is confined to gymnasiums, health clubs, and the like wherein a plurality of athletes may be exercising at once.
Another possiblity for exercise apparatus is shown in U.S. Pat. No. 4,200,280 to Goodwin, which seems to correspond to that sold under the trade name "Bodybar". This apparatus comprises a vertical station comprising a track on which ride a selectable number of a set of weights which can be lifted by an athlete to exercise his upper body. Another such apparatus, featuring plural attachment points for handles, is shown in U.S. Reissue Pat. No. 28,066 to Marcyan. The Goodwin machine may also be provided with a cable and pulley arrangement for exercise of the legs. This suffers from the defects noted above with respect to the Universal Gym's use of cables and pulleys; that is, that the athlete is not constrained to follow the most efficient or safest path of exercise. Moreover, numerous important exercises such as those for the lower back referred to above are not made possible according to either the Goodwin or Marcyan schemes. See also U.S. Pat. No. 3,708,167 to Potgeiter, which has the same defects.
In addition to this prior art, all of which relates to various machines for providing a plurality of ways in which weights can be lifted against the force of gravity, exercise apparatus has also been shown in the prior art such as U.S. Pat. No. 4,200,281 to Wang in which effort is exerted against a resilient means, such as a spring or other flexible member, or against friction means. See also U.S. Pat. No. 4,183,520 to Chase. Such apparatus suffers from the extremely significant defect that it is impossible to measure the work done by the athlete. Inasmuch as precise measurement of the work done from day to day so as to regulate one's athletic output is essential to achieving the goals of a proper exercise program, such machines which provide plural ways in which to perform work against a resilient means are not suitable for the physical training of an athlete.